1. Field of the Invention
The invention generally relates to a positioning mechanism, and in particular relates to a positioning mechanism for reflectors in a scanner.
2. Related Art
In an image scanner, the document or picture to be scanned is illuminated partially and sequentially by a light source. The reflective light is then collected by detectors via some reflectors, transformed into digital signals and processed into digital image through a computer, a printer, or the like. The positions of the reflectors are quite important to the image acquirement. When a reflector is not in position, the reflective light cannot correctly come to the detectors.
In a conventional scanner, the reflectors are mainly positioned by injection-molded plastic parts, only resilient members, or resilient members incorporated with sheet metal parts.
The injection-molded plastic parts are like those disclosed in U.S. Pat. No. 4,984,882. However, because of the material characteristics and injection limitation, the precision of plastic part is not good enough.
The only resilient members are like that disclosed in U.S. Pat. No. 6,098,947. The resilient member is made of metal and fixed at its rim by hooks or screws. Though the resilient member is easy to be mounted, it is mounted on a carrier of optical module of the scanner that is made of imprecise injection-molded plastic. Therefore, the positioning is unsatisfied.
A better way of positioning is to mount an angular fixing plate on the carrier first. The angular fixing plate includes a supporting surface for the reflector to mount to. Then, the reflector is fixed by a resilient member. Because the angular fixing plate is made of metal, it provides a better positioning of the reflector. However, the arrangement uses more components and needs more complicated assembly process and higher manufacturing cost that are disadvantages to the price and competition. Furthermore, in order to simplify assembly process, the assembling of reflector is preferred of a tool-less operation.